1. Field of the Invention
There are several, if not many, types of medical problems wherein the favored treatment calls for the administration of medicaments either at frequent intervals or at rates which are comparable to the protective and defensive reactions of certain body organs. Rapidly accumulating clinical evidence from humans and data from research using laboratory animals have led many diabetologists--that is, internists specializing in the diagnosis and treatment of diabetes--to believe that poor control of blood glucose levels is the prime factor in the development of later complications of diabetes. The goal of insulin therapy is to approximate pancreatic insulin secretion as closely as possible in order to avoid excessive swings in blood sugar levels. But with conventionally administered insulin, normal glucose levels (normoglycemia) are rarely attained, even in a hospital setting, and many severely insulin-deficient patients seldom or never have a negative urine glucose. The short-term consequences of poorly regulated intervals of hyper- and hypoglycemia are well known (irritability, lethargy, depressions, appetitive changes and so forth), but it is the long-term consequences which lead to the terrible consequences of chronic diabetes.
The preferred therapeutic approach is to deliver insulin in quantities as close to physiologic demand (the way the normal pancreas operates) as possible. Furthermore, clinical evidence indicates that maintenance of normal blood glucose levels might prevent the vascular complications or perhaps even reverse those already developing if caught early enough.
Slow, long-continued injections of medicaments for cancer chemotherapy, chronic pain therapy, hormonal deficiencies (other than from pancreatic failure) plasma infusion, and certain genetic diseases are also in need of means for the reliable automatic slow (but adjustable) delivery of medicaments.
2. Description of the Prior Art
The patented prior art presently known to applicant includes the following:
Kollsman U.S. Pat. No. 2,605,765, Aug. 5, 1952 for an Automatic Syringe which is portable and designed to effect subcutaneous injections at a predetermined rate.
Gidlund U.S. Pat. No. 3,349,767, Oct. 31, 1967 for an Injection Syringe adapted to introduce "great quantities" of liquid rapidly, as for x-ray contrast photography.
Hodosh et al., U.S. Pat. No. 3,768,472, Oct. 30, 1973 for a Fluid Dispensing Gun, a complicated mechanism adapted to shoot novocaine into a patient in aid of a surgical or dental procedure.
Kamen U.S. Pat. No. 3,858,581, Jan. 7, 1975, for a Medication Injection Device providing a motor-driven syringe for repetitive medication injection.
Bron et al., U.S. Pat. No. 4,007,739, Feb. 15, 1977 for a Fluid-Operated Hypodermic Syringe, particularly for medication of livestock.
Citrin U.S. Pat. No. 4,022,207, May 10, 1977, for an Actuator for a Syringe intended to dispense precise liquid quantities in an accurately repeatable manner, with single-hand control.
Wagner U.S. Pat. No. 4,114,619, Sept. 19, 1978 for Automatic Injecting Apparatus wherein the patient's skin is drawn into a tensed position against the needle tip before a hypodermic injection is performed.
Wuthrich et al., U.S. Pat. No. 4,059,110, Nov. 22, 1977 for a clockwork driven hypodermic syringe; the patent cites and discusses several prior patents on "mechanically-powered hypodermic syringes for medical or laboratory purposes" (including Kollsman, supra) and dismisses them as not pertinent to the invention which Wuthrich characterized as "relatively small and portable . . . comparatively simple to manufacture, and inexpensive."
Portner et al. U.S. Pat. No. 4,265,241 for an Implantable Infusion Device describes several embodiments each relying on externally transmitted signals to release doses of a medicament from a variable volume implanted container.